As I understand it, Newton's rings occur when two smooth surfaces come into contact with each other. The Trix is designed to accommodate retouching on either surface, it has a tooth or texture to hold the spotting dye or pigment as does the coated surface of the Anti Newton glass. On the top position in the carrier and facing down it comes into contact with the smooth back of the film, and doesn't allow complete contact with the film and prevents Newton's rings. In the cast of some Tmax emulsions or thin, under exposed emulsions, the emulsion side of the film is allowed to come into more complete contact with the smooth uncoated bottom glass plate and creates Newton rings on the bottom interface. The method of coating Anti Newton can very from spraying on a coating to sandblasting the glass or chemically etching the glass. We also used lithographer's powder lightly dusted on the top glass plate to make the film stand off from the top glass plate (lithographers powder was finely ground glass)! Rosinor powder, corn starch baby powder or talc can do the same thing, just lightly dust it on and you have a temporary AN surface.